The present invention relates to the field of vibration testing, and more particularly to the field of combined vibration testing and centrifuge testing of electromechanical subsystems to verify capabilities in rocket launch environments.
Vibration testing is a technology that has many applications in industry. Many manufactured products are subjected to high frequency vibrations (up to 3 kHz) to determine the reliability of the products in a vibration environment. Moreover, in simulating a rocket launch environment, vibrations are imposed on the tested item in the presence of acceleration forces. More specifically, rocket powered missile launch presents a variety of acceleration force and vibration force environments which stem from missile launch, powered flight, and reentry. Many manufactured products form the onboard control systems and the payloads of rockets and rocket powered missiles, and such products are tested as to their capabilities in the rocket launch environment.
Presently, ground testing evaluation techniques are known which simulate a rocket launch environment and which employ centrifuge test devices that permit the addition of vibrational forces. One such known technique employs an electrodynamic shaker which is positioned in an in-line or cross-arm configuration on a centrifuge to provide selectable vibration directions. A problem, however, associated with this technique is the presence of an internal bearing or other forms of side load restraints which inherently impose undesirable limitations on the shaker performance. More specifically, the shaker is prevented from providing a precisely controllable, broadband vibration environment in the presence of the centripetal force created by the centrifuge. It would be desirable, therefore, to provide a precisely controllable, broadband vibration environment in the presence of centripetal force to permit a more accurate simulation testing environment for testing parts in a variety of acceleration and vibration conditions experienced in rocket launch, powered flight, and reentry.
Another known ground testing evaluation technique which simulates a rocket launch environment employs two electrodynamic shakers and a slip table to provide vibration to test items on a centrifuge. This technique is hampered by distortion of acceleration waveforms and decoupling of the vibratory motion. The two shakers are rotated on the centrifuge arm to produce the various vibration lines of action.
Generally speaking, the known testing techniques employing electrodynamic shakers on centrifuges provide undesirable distortion of vibration frequencies. It would be desirable, therefore, to provide an apparatus that employs an electrodynamic shaker that provides high fidelity and undistorted vibrations to the item under test on a centrifuge.
Moreover, the known testing techniques employing vibrations imposed on centripetal forces do not provide precisely controllable vibrations in a high frequency range (up to 3 kHz). It would be desirable, therefore, to provide a testing apparatus that provides precisely controllable high frequency vibrations to a test item in an environment experiencing centrifugal forces.